JWSS - Journal of Water and Soil Science

Surge tanks and air chambers are the most useful solution to deal with water hammer in water transmission systems (WTS). The optimal design of these protective devices can be effective in reducing the costs of constructing and operating a water transmission system. In this article, some software with the capability of simulating and optimizing these protective equipment is presented. To simulate the behavior of the system in the transient condition, the characteristic method was used. To optimize the number, dimensions and location of the surge tanks and air chambers, the genetic algorithm was employed. Constraints of the problem included the control of negative and positive pressures within the permissible range to prevent the cavitation and water hammer. To test the performance of simulation and optimization models, a well-known water transmission system in the previous research was selected as a case study. The results indicated that the critical heads were damped to a safer and allowable range; also, the total cost of the surge tanks and air chambers was reduced by 17% by the proposed method.

Water hammer is one of the unsteady flows in urban water distribution networks, which has been of great importance due to the damage caused to the pipeline and has always been of interest to researchers. In this study, the phenomenon of water hammer due to the sudden closure of the valve in the downstream end has been investigated in a laboratory and using a numerical model. In the laboratory section of the study, the effect of flow changes with control equipment and without control equipment on the maximum and minimum height of pressure wave head was investigated. The results showed that the proper performance of the surge tower pipe in reducing the maximum pressure wave as well as improving the negative pressures in the system. In a maximum discharge of 35.75 liters per minute, surge tower pipe reduced pressure wave head by a maximum of 70.40%. In a minimum discharge of 7.70 liters per minute, the surge tower pipe reduced the height of maximum pressure by 34.82%. Also, in minimum discharge, surge tower pipe has improved the minimum pressure wave head by more than 78%. AFT Impulse numerical model was used to analyze the water hammer. The results of the numerical model were examined in a benchmark problem using a characteristic method and its validity was confirmed. Simulation of laboratory model with numerical software showed that this software only predicts the first wave properly when water hammer produces negative pressures, but in the next cycles it does not show the depreciation rate of the pressure wave, properly.